Functional Programming for the Object-Oriented Programmer. Brian Marick For more about what the book covers, see the sample PDF. Once upon a time, object-oriented programming was a radical . In the PDF version, links within a book appear as colored text, and links to. Functional Programming for the Object-Oriented Programmer by Brian Marick ( ndolefideshal.tk) ndolefideshal.tk~rwh/plbook/ndolefideshal.tk
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This makes functional programming much harder to learn. I come here discuss programming. There are certainly a number of ways to write write something in either paradigm. The number of ways you can write something is a horrible metric to evaluate languages on.
Any sufficiently clever programmer can come up with a number of bad solutions. The useful imperative techniques are more obvious to you because you have more experience with that framework. Experienced functional programmers would just as quickly narrow their list of useful solutions. In order to be productive in a functional style, you don't need to know much of the language's standard library.
You simply write small functions that can be applied in a number of areas. You'll probably end up re-inventing the wheel though, as most functional languages come with most of the essential functional constructs included in the standard library.
If anything, functional programming is more beginner friendly, because you don't end up dealing with mutable state and you can easily work on the level of abstraction that you're most comfortable with you're just composing ever more advanced functions from simpler ones.
Most of these are not not what a "reasonable programmer" would do. An unreasonable programmer would be able to screw up on any paradigm. You'd probably have even more ways to screw up like this with an OO language, creating classes for recursive functions, trampolines, a pattern matching class, implement an language interpreter inside your factorial implementation, etc. You assertion on how many ways one could screw up on OO is irrelevant and besides, you'd really need a good understanding of OO to even try implementing those.
I didn't mean to use to imply any of those methods were bad. I have revised my post so people can't miss the point.
Now, addressing your concerns. All of the examples except for few particularly egregious ones seems reasonable to me.
I'm sure there's more that's as elegant if not more elegant ways to do the same thing. You could translate those to an OO language quite easily too, though with a lot more code.
For example, what foldl does, from my understanding, is to recursively apply a function to both a starting value and the first element of a list, and then the same thing again, where the result from the last call becomes the starting value and the rest of the list becomes the list we're working on, up until the list is empty.
Not sure if I've explained this well but I've not been into this long.
If you see the second function, that's what it's doing, except it's working just with numbers and not a list. Since foldl works on lists, you need an enumerator, which in this case is just 1 through to n. The sixth example is great here. Product could easily be an abstraction on something quite similar to three, which itself could very well be an abstraction quite similar to two using lists, functions to deal with lists and a given function.
Please correct me if I'm wrong at any point here. I'm looking to improve these skills quite a lot so it'd be very, very welcome. You got the core, I will correct your edges.
The [ And no foldl is not an abstraction of 2 because foldl is tail recursive while 2 is not. One of the selling points of object-oriented programming, as promoted by its advocates, is that separation of concerns and loose coupling see below enable teams to work on large systems more effectively.
It is not a hard-and-fast set of rules or a specific methodology. Different programming languages approach OOP differently. Some are more or less strict, and some are just different. What follows is a general overview of object-oriented design concepts. See our sister article, Object-Oriented Programming for resources and details that explain how these concepts are implemented in many different languages.
Separation of Concerns The central guiding principle which informs all the other concepts in object-oriented programming is separation of concerns.
This is the idea that logically distinct bundles of data and functionality should be separated into distinct bundles of application code. This idea is not unique to object-oriented programming. Most programming languages allow for separation of concerns, and most programming paradigms promote it.
However, separation of concerns is of special importance to object-oriented programming. Strong separation of concerns is the impetus behind nearly all other OO concepts.
Objects and Classes It seems, at first, that the fundamental concept in object-oriented programming is objects. A class defines an object; an object instantiates a class.
There are a lot of customers, but they all do the same thing. So there would be a Customer class, in which the programmer defined what a customer is, and how it works. Then, each individual customer is represented in the system by a customer object. Since class definitions specify all the implementation details, most of the work of developing an object-oriented program involves working with classes, not objects.
These are things that the object is capable of doing, and are also defined within the class. One of the challenges of developing good object-oriented programs is determining how to split up functions among several potential classes.
For example, should a checkout method belong to the Customer or to the Shopping Cart? Understanding that ecommerce needs Products and a project management system needs Projects is pretty easy. But large object-oriented programs have countless classes defining all sorts of abstract bundles of functionality, like object relational mappers, object factories, and controllers just to name three easy-to-understand examples.
Navigating these concerns takes practice, of course. An object-oriented developer can also be aided by an understanding of design patterns, and by a development process that includes modeling.
Here are a few resources to help you better understand class, properties, and methods: Classes, Objects, Properties, and Method Concepts is a great minute video overview of these concepts; Choosing Between Properties and Methods is a. NET tutorial, covering some design considerations which are applicable to any language; Understanding Classes, Methods, and Properties in C provides a good explanation, with some helpful diagrams.
Message Passing and Dynamic Dispatch Classes, and a number of other concepts covered here, have become inexorably linked to object-oriented programming. However, according to the computer scientist who coined the term , object-oriented programming is about message passing.
Message passing means that objects communicate with each other by sending messages. This sounds trivial, but it affects how function calls are made.
The message contains a method name and any associated parameters. The called object then has the ability to handle that method call however is needed. This ability for each object to determine its own response to method calls as needed is called dynamic dispatch.
It allows objects to evolve over run time, and respond to messages according to their present state.